The present disclosure relates to a developing device for developing an electrostatic latent image on an image-carrying member by causing the image-carrying member to hold toner, and to an image forming apparatus including the developing device.
An image forming apparatus, such as a copier, a printer or the like, that forms an image on a sheet of paper by the electrophotographic method is provided with a developing device. The developing device uses toner to develop an electrostatic latent image formed on an image-carrying member such as a photosensitive drum. As the developing method, there is known a so-called two-component developing method that uses two-component developer composed of magnetic carrier and toner to develop a toner image on the image-carrying member. According to a typical two-component developing method, a developing roller and a magnetic roller are used, wherein the developing roller is arranged at a predetermined distance from the image-carrying member, and a magnet is provided inside the magnetic roller. According to the two-component developing method, only non-magnetic toner is transferred onto the developing roller while the magnetic carrier is left on the magnetic roller, so that a toner thin layer is formed on the developing roller. An AC electric field is then supplied to cause the toner to be flied from the developing roller onto the electrostatic latent image formed on the image-carrying member, so that the toner adheres to the electrostatic latent image.